LEGAZPI, Philippines (AP) -- A volcano in southeastern Philippines spewed lava and clouds of ash Thursday as officials stepped up evacuations, warning that a more powerful eruption could come at any time.

The pre-dawn eruption sent a glowing river of lava part way down Mayon Volcano's slope and rained ash over several villages. There were no immediate reports of injuries.

Officials called for more residents near the mountain to evacuate. At least 4,150 people from 14 villages had fled their homes as of noon Wednesday, said Cedric Daep, head of the Albay provincial disaster management office.

For about a week, the mountain has been emitting ash plumes and occasional flows of lava. The crater's lava dome has swelled, occasionally sending molten rocks the size of automobiles crashing down the 8,100-foot volcano.

Ernesto Corpuz, chief of volcano monitoring at the Philippine Institute of Volcanology and Seismology, said the continuing supply of magma to the dome suggests that volcanic activity will intensify, leading to an explosive eruption.

Mayon, known for its conical shape, is about 215 miles southeast of Manila in Albay province.

Most residents of the village of Bonga, directly in the path of a possible lava flow, have been evacuated, but many men stayed home to watch over crops and farm animals.

Florentino Mina, a 60-year-old farmer who survived five previous eruptions, said he was confident he could escape another since he and his neighbors have several vehicles ready in which to flee.

The volcano has been showing signs of unrest since last June, spewing ash-laden smoke high in the sky several times last year, but causing no injuries. An explosion in September forced more than 5,700 people to flee their homes.

Mayon's most violent eruption on Feb. 1, 1814, killed more than 1,200 people and buried an entire town in volcanic mud flows. Its last eruption in February 1993 killed more than 70 villagers.